Korean Patent No. 656,811 (Korean Patent Application No. 10-2006-0006902, filed on Jan. 23, 2006) granted to the Applicant of the instant application, from Korean Intellectual Property Office, disclosures of which are hereby incorporated by reference, discloses an “overdrive system of a taxi-type bicycle.” FIG. 1 shows an overdrive system of a taxi-type bicycle having a plurality of sprockets and ratchet wheels.
As shown in FIG. 1, in case of the overdrive system, where a user steps on a forward pedal 51 of a forward lever 50, a ratchet wheel 29 joined to an end portion of the forward pedal 51 rotates a shaft 41, a first ratchet wheel 21 connected to the ratchet wheel 29 via a first chain 31 is rotated, and a second large-scale sprocket 12 or a fifth ratchet wheel 25 is also rotated to thereby rotate a rear wheel 92.
However, since a distance ranging from the forward pedal 51 of the forward lever 50 to the ratchet wheel 29 is long, the bicycle having the overdrive system with the above-mentioned structure may not be rapid when the user steps on the forward pedal 51 because a rotational displacement of the ratchet wheel 29 is small.